A plant DNA-binding protein increases the number of active preinitiation complexes in a human in vitro transcription system.
TGA1a is a tobacco DNA-binding protein that binds to the activation sequence-1 (as-1) element of the cauliflower mosaic virus 35S promoter. We have produced TGA1a in Escherichia coli, purified it from bacterial extracts, and examined its effect on transcription in a human in vitro system. Addition of TGA1a stimulates transcription by up to 20 times, and the stimulation is dependent on the presence of the as-1 element in the promoter. When transcription reinitiation is inhibited by 0.3 M KCl, activation is similar. Therefore, TGA1a activates transcription by increasing the number of active preinitiation complexes. After formation of the preinitiation complexes in the presence of TGA1a, oligonucleotides containing TGA1a-binding sites do not significantly affect the stimulated level of transcription. This result indicates that a complex remains committed to the promoter site after initiation and that this complex is used repeatedly during several initiation events. Our study demonstrates for the first time that a plant factor can activate transcription in a human in vitro system and that the activation mechanism of the plant factor is similar to that of mammalian factors.
Katagiri
F
F
Laboratory of Plant Molecular Biology, Rockefeller University, New York, New York 10021-6399.
Yamazaki
K
K
Horikoshi
M
M
Roeder
R G
RG
Chua
N H
NH
D000595:Amino Acid Sequence; D001483:Base Sequence; D050976:Basic-Leucine Zipper Transcription Factors; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D005786:Gene Expression Regulation; D007700:Kinetics; D008969:Molecular Sequence Data; D009029:Mosaic Viruses / Q000235:genetics; D015345:Oligonucleotide Probes; D010940:Plant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D010944:Plants / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D015183:Restriction Mapping; D014158:Transcription, Genetic
D050976:Basic-Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins; D015345:Oligonucleotide Probes; D010940:Plant Proteins; D011994:Recombinant Proteins; C065794:TGA1a protein, Nicotiana tabacum